Processing and Characterization of Oxygen Sensors Prepared From Freeze-Dried Calcia-Stabilized Zirconia Powders

Precursor powders of 15 and 22 mol% calcia-stabilized zirconia solid electrolytes were synthesized by a freeze-drying method and calcined at 900°C. Sensor elements were fabricated via uniaxial pressing of the calcined powders and subsequently sintered at 1650°C. X-ray diffraction and scanning electron microscopy techniques were used to analyze the phase composition and microstructure. The electrical response of the gas sensors to oxygen and the complex impedance in air were investigated at various operating temperatures. The correlation between electrical properties and sensor material chemical compositions as well as microstructure is discussed.